1. Field of the Invention
This invention relates to a so-called biocapsule obtained by allowing a microorganism to capture useful substances and confine them therein.
2. Description of the Invention
So-called microcapsules consist of a liquid, solid or gas in the form of fine particle of 1 .mu.m to several hundreds .mu.m and a thin film covering the fine particle and having a thickness of several m.mu.m to several .mu.m. Since the first disclosure in U.S. Pat. Nos. 2,711,376 and 2,712,507, these microcapsules have been used in various applications. Their most common application is pressure-sensitive recording papers. In this application, microcapsules containing a color former solution obtained by dissolving a colorless, electron-donating dye precursor (color former) in a non-volatile solvent are coated on the back side of a substrate to form an upper paper; a colorless, electron-accepting acidic substance (color developer) is coated on the top side of another substrate to form a lower paper; these two papers are superimposed so that the coated sides face each other; and manual writing or typing is applied onto these papers from the side of the lower paper, whereby the microcapsules are broken, the microcapsule contents are released, the color former and the color developer contact with each other to cause a chemical reaction, and a colored substance is formed on the surface of the lower paper as a copy image. Thus, in microcapsules, useful substances having particular properties are confined in a thin film; therefore, even their particular properties can be simultaneously confined, and the substances can be taken out whenever necessary by breaking the thin film.
Two substances reactive to each other can be separated by way of microencapsulation and accordingly can be stored together over a long period of time without causing any reaction, and their reaction can be started only by breaking their microcapsules. Having such favorable functions, microcapsules have been extensively used in applications such as recording materials, medicines, foods, cosmetics, adhesives, agricultural chemicals, artificial internal organs and the like.
The microcapsules used in the above applications are produced in accordance with encapsulation processes such as coacervation process, interfacial polymerization process, in situ process, spray drying process, curing-in-liquid process and the like and their wall membranes are composed of gelatin or a synthetic resin.
In constrast to the above encapsulation processes, there is an encapsulation process using, as a wall membrane, a completely different material, namely, a microorganism. Capsules produced according to this process are called biocapsules or microorganism capsules. Biocapsules are disclosed in, for example, U.S. Pat. No. 4,001,480, Japanese Patent Application Kokai (Laid-open) No. 107,189/1983, etc. U.S. Pat. No. 4,001,480 suggests a process for preparing an encapsulated cosmetic by contacting fat-soluble substances with an Eumycete containing a very large amount of natural fats. According to this patent, said substances must be soluble in the natural fats or lipids of said Eumycete and further the Eumycete must contain natural fats in an amount of about 40 to 60% by weight. Furthermore, the Eumycete used is limited to grown Eumycetes, namely, Eumycetes having a propagative ability. Japanese Patent Application Kokai (Laid-open) No. 107,189/1983 suggests an encapsulation process wherein a grown microorganism containing lipids in an amount of 10% by weight or more (e.g. a fat yeast, a beer yeast or the like) is treated an organic substance for increasing lipids in said microorganism (e.g. an aliphatic alcohol, an ester, an aromatic hydrocarbon, a hydrogenated aromatic hydorcarbon or the like) to allow said microorganism to ingest and stably contain the organic substance. The grown microorganism used above refers to a microorganism recovered from the culture medium and preferably contains a considerable amount of lipids, particularly 10% by weight or more and, for example, 20 to 35% by weight.
Thus, the microorganism used in Japanese Patent Application Kokai (Laid-open) No. 107,189/1983 is a grown microorganism, namely, an organism having a propagative ability and must contain lipids in an amount of 10% by weight or more, preferably 20 to 35% by weight or 40 to 60% by weight. This requires a prodigious labor for maintenance and storage of microorganism as well as a care for maintenance of lipid content in microorganism.
Hence, it has been desired to develop a process for producing more easily and at a lower cost a pressure-sensitive biocapsule which can preferably used in pressure-sensitive recording papers, medicines, foods, cosmetics, adhesives, perfumes, catalysts, agricultural chemicals, etc.
Meanwhile, there are photohardenable microcapsules. In these microcapsules, microcapsule breakability necessary for releasing the contents can be controlled to any desired level, for example, unbreakable, partially breakable or totally breakable.
The photohardenable microcapsules contain, as major components, a photohardenable resin and a photopolymerization initiator and the breakability of the microcapsules is controlled by the amount of light applied thereto.
The present inventors previously disclosed a photohardenable microcapsule in Japanese Patent Application Kokai (Laid-open) No. 14,943/1983, wherein there were mentioned, as the microencapsulation process for said photohardenable microcapsule, the phase separation process (U.S. Pat. Nos. 2,800,457 and 2,800,458), the interfacial polymerization process (Japanese Patent Publication Nos. 19,574/1963, 446/1967 and 771/1967), the in situ process based on monomer polymerization (Japanese Patent Publication No. 9,168/1961 and Japanese Patent Application Kokai (Laid-open) No. 9,097/1976), the melting-dispersion-cooling process (UK Pat. Nos. 952,807 and 965,074) and the spray drying process (U.S. Pat. No. 3,111,407 and UK Pat. No. 930,422), which were all known at that time.
The above mentioned microencapsulation processes for photohardenable microcapsules, however, have drawbacks such as, for example, use of costly membrane materials, need of polymerization, complicated production process and high cost of produced microcapsule. Therefore, it has been awaited to produce photohardenable microcapsules using the previously mentioned bioencapsulation process because such production will not only have no drawback as mentioned above but also provide a big economical advantage.